In order to produce multiple chokes, several windings insulated from one another are wound onto toroidal cores along a periphery. In order to ensure the electrical insulation between the windings, one or more electrical isolations are provided in the interior space of the toroidal core. The winding space located in the interior of the toroidal core is thus preferably divided into several winding spaces of equal size.
Since the toroidal cores are resintered during production with an insulation, the resintered cores exhibit relatively marked deviations from one another in respect of their inner diameter. An electrical isolation is intended to compensate for these tolerances as far as possible.
It is known to place the toroidal core onto a holding device with injection moulded insulating webs. This has the drawback that the electrical isolation cannot be fitted until after the winding-on. In the case of chokes with a high number of windings, which have to be arranged in two or even more layers on the toroidal core, no space or only very little space thus remains for the subsequent fitting of the injection moulded insulating webs.
Furthermore, it is known to insert two pressboards into one another and then to install the same in the toroidal core. This has the drawback that the boards can be slightly displaced by the winding tension during winding-on. The effect of this would be that the winding spaces would diverge from one another in their size. As a result, it would not be possible to arrange several windings of equal size on the choke making optimum use of the available space.
According to another known technique for producing the electrical isolation, several plastic boards are clamped against one another in the core hole, i.e. in the interior of the toroidal core. This has the drawback that the arrangement of plastic boards only becomes properly stable after the fitting of the last board. Moreover, this has the drawback that a relatively high outlay is required for the fitting.
It is further known to use toroidal cores in plastic troughs or cores injection-coated with plastic with moulded grooves for receiving rigid plastic insulating webs or plastic insulating crosses. The tolerances of the core inner diameter are compensated for by the plastic shell. Such an arrangement has the drawback that valuable winding space is lost on account of the plastic sheathing. Furthermore, there is the drawback that the sheathing is cost-intensive in production due to its complex geometrical shape.